SAN DIEGO -- Dorothy Marian Shelton, 57, who lobbied for families of missing servicemen as the wife of the last American still listed as a prisoner-of-war in Southeast Asia, has died in an apparent suicide.

Police said Friday that Mrs. Shelton died Thursday night from an apparently self-inflicted gunshot wound to the head.

Family members said she left a note at her home professing her love for her five children, but it did not mention her husband or offer an explanation for her death.

Mrs. Shelton's quest to learn her husband's fate took her to the jungles of Laos and the halls of Congress in the unwavering belief that Air Force Col. Charles E. Shelton was still alive.

Shelton, then a captain, was shot down over Laos on April 23, 1965, and captured a few days later.

A Pentagon spokesman, Edward Lundquist, was quoted this summer as saying the military believed Shelton died in the 1960s from malaria or dysentery.

But the U.S. government made Shelton a symbol, promoting him, leaving him on the official rolls as a prisoner of war and sending an "active duty" pay check to his wife every month.

About 2,500 other men unaccounted for in Southeast Asia have been listed as presumed dead.

For 25 years, Mrs. Shelton pressured legislators for help; traveled the world seeking information about her husband; and appeared on numerous radio and television programs, urging the government to provide more answers to families of the missing.

"She spent a lot of time looking for answers and couldn't find them," said retired Navy Capt. Red McDaniel, a POW for six years. "But her death will strengthen the resolve of a lot of people. This issue will not go away."